Loud speaker



'LOUD SPEAKER- FiledApril 21. 1924 WITNESSES: INVENTOR do /i 5/9 @XW grep ,0/0/1 v Patented Sept. .27, 1927.

UNITED STATES :PATENT' OFFICE.

JOSEPH SLEPIAN, OF SWISSVALE, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, ACOBPORATION' OF PENNSYLVANIA.

LOUD SPEAKER.

Application filed April 21, 1924. Serial No. 707,847.

This invention relates to sound-reproducing devices, such as loud speakers used in connection with radio-reception work and telephone receivers used either in such connection or in ordinary telephony.

It is -an object of this invention to provide a translating device which shall be free from resonance periods.

It is a further object of this invention to produce a sounding device in which the sheet member, instead of being flexed, as a diaphragm usually is, moves bodily to establish the acoustic vibrations.

It is a further object of this invention to provide a sounding device in which the force for actuating the sheet member shall be applied over a large portion of the surface of said member thereby avoiding flexure of the sheet member.

It is a further object of this invention to make use of the principle by which eddy currents react with a magnetic field to cause a'mechanical force upon the conductor in which the eddy currents occur.

It is a further object of this invention to provide a. sounding device in which the sheet member which produces the acoustic vibrations'shall have sufiicient area to cause ample sound without the necessity of a horn or analogous structure for enhancing the acoustic action. 1 It is a further object of'this invention to provide the above-mentioned area without making the instrument, as a whole, of large dimensions.

It is a further object of this invention to so arrange several sheet members, each of which acts upon the air that the air pressure developed by the movement of one member shall be communicated to the next, andso on, whereby the power acoustically radiated om the final member shall be approximately the sum of all the power delivered by the several sheet/members.

Other objects of this invention and details of the'st-ructure employed will be apparent.

from the following descri tion and the accompanying drawing in w ichz' Fig. 1 is a diagram illustrating the con nections employed and showing a bottom view of the translating instrument,

A telephone transmitter 1 is connected to a circuit which includes the battery 2 and the choke coil 3. The circuit also includes a coil 4, which is'preferably flat. This coil is shown as rectangular, but a. flat coil of any other shape will serve equally well.' Resting upon the coil 4, is a sheet 5 of conductmg material, for example, a sheet of-gold leaf or of gold leaf reinforced by having .cardboard or other light and strong sheet material cemented to it.

Preferably the coil 4 occupies a horizontal posltlOIl and the coil and sheet are surrounded by a frame or other means for restraining the sheet from edgewise movement, but neither of these details is indispensable.

The coils may be divided into several superposed coils as shown in Fig. 3. Such colls are connected in series as indicated at 6 and 7, and the surrounding frame 8 incloses the whole pile of coils and sheets. One of the sheets 5 rests upon each of the coils 4.

In theoperation of the device, sound entermg the microphone 1 causes a variation in the current in the coil 4, which corresponds to the sound. This variation is superposed upon the direct current delivered from the battery 2. The inductance 3, by opposing fluctuations in the output of the battery 2, insures that the changes in the resistance of the microphone 1 will be faithfully reproduced by changes in the current in the coil 4.

The coil ,4, produces a magnetic field, due

tween the ma sheet is returned toward the coil 4, not only by gravity but also by the interaction beetic field and the eddy currents. The e dy currents, during the sec ond half-cycle, are in the opposite direction and so force acting upon the sheet is in the opposite direction. 2' l The force developed by the interaction between the eddy currents and the magnetic field is produced practically all over that portion of the sheet which is adjacent to the coil. Preferably, although this is not absolutel essential, the coil extends nearly to the boundaries of the sheet. Consequently, the forces developed tend to move the sheet, as a whole, without moving one part more than aliother and so flexing the sheet. The natural period of vibration'of the sheet does not, therefore, enter into the determination of its motion. For this reason, the instrument'is without any resonant period and will, therefore, reproduce sounds of all fre uencies with equalfaithfulness,

If the s eet be of suflicient area, a large body of air will be set into motion by the motion of the sheet. A very considerable ower will thus be acoustically radiated.

ith a sheet of sufiicientarea, it is, there-.

fore, unnecessary to. provide a horn or other device for producing acousticloading of. the

sheet or otherwise enhancing the acoustic radiation.

In order to provide suflicient acoustic ,ac-

sheet may be divided into superposed por-- tions as described in'connection with Fig.

'- it. The second sheet is thus lifted b 3. The upward movement, given to the bottom sheet in this figure by. the bottom layer of the coil, tends to compress the air between this sheet and the one next above two forces, namely, the air pressure and t e action of the second la er of the coil. It thus delivers to the third sheet, the sum of the forces exerted bythe bottom layer of the coil and thesecond layer of the coil.

This additive action continues throughout the succession of layers. The top sheet, consequently, exerts upon the -external atmosphere, a force which is nearly equal to the sum of the forces obtained from each of the several layers of the coil. During the half-cycle in which the forces exerted bythe layers upon the sheets are downward, a similar additive action takes place, so that the lower sheet exerts a downward'pressure upon the external atmosphere which is substantially the sum of the results of the-actions of the several motions. I

Many modifications of the device will be apparent to those skilled in the art. The small number of modifications illustrated and described is not to be taken asa limita tion. No limitation, except that imposed means acting over approximately the whole area of said sheet for causing the sheet to so move.

3. A sound-producing device comprising a coil, a sheet of conducting material su erposed thereon and free to move as a w ole relative thereto, and means for producing varying currents in said coik 4. A sound-producing device comprising a coil, a sheet of conducting material adjacent to, and of approximately the same area as, said coil and free to move as a whole relative thereto and means for producing varying currents in said coil.

5. A sound-producing device comprising.

a free sheet and electromagnetic means for producing forces at an angle to said sheet simultaneously at substantially all parts thereof.

6. Ina sound-producing device, a plurality of superposed coils, sheetsof conducting material, one resting on each coil, said sheets being free to move parallel to the axis of the coils and constrained from other movement, and means for producing signal-controlled currents in said coils.

7. In a sound-producing device, a plurality of superposed coils, sheets of conducting material, one resting on each coil, said sheets being free to move parallel to the axis of'the coils and constrained from other ing currents in said coils.

8. In a sound-producing device rality of superposed stationary coils, sheets of conducting material, one resting freely on each coil, saidsheets being free to'move parallel to the. axis of the coils and constrained from other movement and means foir1s producing pulsating currents in said co 9. In a tele hone instrument, means for producing a 'rect magnetic field with a. periodic magnetic field superposed thereon, and a sheet of conductive non-ma etic material constrained to remain within the influence of said field and free to move under said influence.

- 10. In a sound-producing device, a plumovement and means for producing pulsatrality of superposedand spaced sheets, each free to move at an angle. to its plane, Slga plu-" nus-191' -a on each sheet, and a pneumatic connection currents are produced in said diaphragm, between the sheets, whereby said forces act said diaphragm being free to move under 10 additively. the reaction between said eddy currents and 11. In a telephone instrument, a diasaid field. 5 phra of "non-magnetic conductive, ma- In testimony whereof, I have hereunto teria means for producing a magnetic subscribed my name this 9th day of April,

field through said dia hragm means for 1924. varying the magnetic eld, whereby eddy JOSEPH SLEPIAN. 

